I second having a test kit & reviewing what roles KH, GH, pH, nitrites, and nitrates play in water quality. As said, cycling the tank is a must. When you are just starting out, without any fish yet, it’s possible to do what I think is called a ‘soft-cycle’ (not sure if that’s the correct term) using materials to get the cycle started instead of fish poo/pee, definitely research that. Live plants (depending on species) often undergo a ‘melting’ phase after being added to an aquarium- learn about this and get your plants fully established prior to putting any animals in. I recommend buying plants from an online supplier and not a big chain store. I have used all kinds of filters and most of them work just fine, they just have differing otis and cons. Make sure you have a ‘drip loop’ where your aquarium electrical equipment is plugged in so you don’t electrocute yourself (I have done that as a child and it sucks). If you need to change conditions in the aquarium, do it gradually.
If you use tap water, make sure you know how to treat it properly. Research the different methods of filtration and pick an approach, making sure to consider the appropriate levels of surface agitation and water flow strength. ALWAYS fill the aquarium completely full with water for at least 48 hours to test for leaks before doing anything else. Know how many fish and of what species and size can be housed safely in the desired aquarium size and don’t exceed that. Don’t use random material from outside in your aquarium. Do research on ‘low tech’ aquariums, but I suggest not starting out by attempting a filterless tank, it’s a more advanced goal. Larger tanks are easier to keep stabilized, though they will still require water changes. More frequent water changes of smaller amounts are much better than Single, very large water changes in most situations (sometimes you need to do huge changes if something bad has occurred). Do not skip out in regular water changes, especially if you have delicate tank residents. If you are just replacing evaporated water, use distilled or RO water, not tap water.
Thicker substrate layers will allow more room for beneficial bacteria to grow. Never use or keep anything (including fish medications or household pipes) with copper in the tank or water added to the tank, as it will kill any invertebrates. Often ‘pest’ snails will arrive on live plants when purchased, I suggest learning about snails in aquariums and decided what your approach to pest snails will be. Any tank previously used for anything other than freshwater fish (e.g., rodents, reptiles) cannot be used for fish. When adding tank inhabitants, always consider their temperament and compatibility. Once your tank is established, if you want to add additional fish or invertebrates, I suggest having a quarantine period. As mentioned, if you keep goldfish, you’ll need a big tank- they poop so much! Make sure you provide the fish with adequate places to hide. If you have any super small or delicate tank residents, make sure the intake to your filter is modified to be safe for them.
Many keepers have a ‘clean up crew’ in their rank to help break down waste/algae/dead plant material, e.g. plecos, otocinclus (probably misspelled), corydoras, snails. etc. I like nerite snails because they eat the algae that may grow on the glass and they can’t breed in fresh water and overrun your tank.
Don’t keep a betta at room temperature and use a heater with a reliable thermostat, buy bettas from a breeder or fish shop and not from a big box pet store chain, make sure you clean and get most of the tannins out of your botanicals prior to putting them in the tank. Bettas REQUIRE access to the surface- if they cannot take breaths if air, they will drown. House ALL bettas alone- betta sorority tanks are suitable for advanced aquarists only, and still often fail. Males will kill each other and eventually females as well. Marimo moss balls in aquariums are a controversial subject, educate yourself about them prior to deciding to purchase any.
I know a moderate amount if a lot of different aspects, did you have a particular aspect you wanted to discuss? Sorry I’m too lazy to edit my comment, I hope I made sense despite jumping around a lot.